The federal Clean Water Act prohibits the discharge of pollutants, including dredged or fill material, into "navigable waters"—statutorily defined as the "waters of the United States"—without a permit (33 U.S.C. §§ 1311, 1344). The U.S. Army Corps of Engineers (the Corps), interpreting EPA regulations, asserted jurisdiction over nonnavigable tributaries and wetlands adjacent to such tributaries. John A. Rapanos filled and leveled wetlands on several parcels in Michigan to prepare for development without obtaining a § 404 permit, despite government warnings. The wetlands on Rapanos's properties were connected to traditional navigable waters only through a series of man-made drains and natural tributaries located miles away. In a related consolidated case (Carabell v. United States Army Corps of Engineers), the property consisted of a 15.4-acre wetland separated from a drainage ditch by a man-made berm; the ditch eventually drained to navigable waters. The government pursued civil enforcement, and the Sixth Circuit upheld the Corps' broad jurisdiction in both cases by deferring to the agency's interpretation that "adjacent" wetlands, even those not directly abutting navigable-in-fact waters, were covered. The Supreme Court granted certiorari and consolidated the cases to decide the scope of WOTUS as to such wetlands.
What is the proper scope of "waters of the United States" under the Clean Water Act with respect to wetlands adjacent to nonnavigable tributaries of navigable waters—specifically, do wetlands lacking a continuous surface connection to navigable waters fall within federal jurisdiction when connected through man-made drains or intermittent channels?
No single majority opinion defined a single controlling rule. The Court produced two principal tests: - Plurality (Scalia, joined by Roberts, Thomas, Alito): The CWA covers only (1) relatively permanent, standing or continuously flowing bodies of water forming geographic features commonly understood as streams, oceans, rivers, and lakes; and (2) wetlands that have a continuous surface connection to such relatively permanent waters such that it is difficult to determine where the water ends and the wetland begins. Ephemeral flows and mere hydrologic connections are insufficient. - Concurrence in the judgment (Kennedy): A water or wetland is covered if it, "either alone or in combination with similarly situated lands in the region, significantly affects the chemical, physical, and biological integrity" of traditional navigable waters—i.e., there is a "significant nexus" between the wetland/tributary and navigable-in-fact waters. Mere adjacency in the Corps' categorical sense is not enough; jurisdiction requires case-specific evidence of significant effects. Because there was no majority, many lower courts applied Marks v. United States to treat Justice Kennedy's significant nexus test as the controlling standard (as the narrowest grounds) or held that jurisdiction exists if either the plurality's test or Justice Kennedy's test is satisfied.
Judgments of the Sixth Circuit were vacated and the cases remanded. The Court did not adopt a single definitive standard for CWA jurisdiction over wetlands. The plurality would require proof of a continuous surface connection to relatively permanent waters; Justice Kennedy would require proof of a significant nexus to navigable waters. On remand, the government was required to establish jurisdiction under one of these approaches.
Plurality (Scalia): Emphasizing textualism and federalism, the plurality read "waters" to mean geographic bodies of water—"relatively permanent, standing or continuously flowing"—rejecting the Corps' expansive interpretation that would transform vast areas of dry land into regulated waters. The plurality distinguished United States v. Riverside Bayview Homes (upholding jurisdiction over wetlands directly abutting navigable waters) and read Solid Waste Agency of Northern Cook County (SWANCC) as foreclosing reliance on tenuous connections or mere use by migratory birds. For wetlands, the plurality required a continuous surface connection to a relatively permanent body of water so that the wetland cannot be readily distinguished from that water. Intermittent or ephemeral channels, subsurface seepage, and remote hydrologic connections do not suffice under this approach. Concurrence in the judgment (Kennedy): Justice Kennedy agreed the Sixth Circuit applied an overbroad adjacency rationale but rejected the plurality's categorical limits. Drawing on Riverside Bayview and SWANCC, he proposed the "significant nexus" test, requiring a case-specific showing that the wetland, either alone or with similarly situated wetlands in the region, significantly affects the chemical, physical, or biological integrity of traditional navigable waters (e.g., pollutant trapping, flood control, sediment retention, or flow moderation). He criticized the plurality's insistence on a continuous surface connection and its exclusion of intermittent streams, noting that ecological functions can be substantial without constant surface water. Concurrence (Roberts): The Chief Justice lamented the absence of a clear, majority rule and urged the agencies to engage in rulemaking to provide clarity, suggesting that with a properly promulgated rule the Corps and EPA could receive Chevron deference. Dissent (Stevens, joined by Souter, Ginsburg, Breyer; plus a separate dissent by Breyer): The dissent would have deferred to the Corps' broad interpretation as reasonable under Chevron, given the CWA's objective to restore and maintain the integrity of the Nation's waters. The dissent argued that both Rapanos's and Carabell's wetlands were within federal authority. Justice Breyer separately urged the Corps to promptly clarify the scope of WOTUS by rulemaking. Practical aftermath: Because no single rationale commanded a majority, lower courts grappled with Marks. Many circuits treated Justice Kennedy's significant nexus as controlling; others held that jurisdiction is proper if either Kennedy's or the plurality's test is met (since at least five Justices would find jurisdiction in such a case). The fractured decision fueled years of regulatory whiplash and case-specific evidence battles over hydrologic and ecological connections.
Rapanos reoriented CWA jurisprudence by rejecting the Corps' most expansive theories and forcing courts to scrutinize the nature of connections between wetlands, tributaries, and navigable waters. It introduced enduring vocabulary—"relatively permanent" waters, "continuous surface connection," and "significant nexus"—that dominated WOTUS debates, compliance counseling, and expert hydrology in litigation. Doctrinally, Rapanos illustrates how fractured opinions can nonetheless supply operative law via Marks and how administrative deference interacts with statutory text, federalism, and scientific complexity. Practically, it drove extensive rulemaking (e.g., 2015 Clean Water Rule, 2020 Navigable Waters Protection Rule, subsequent WOTUS rules) and uneven enforcement nationwide. In 2023, Sackett v. EPA rejected the significant nexus test and adopted an approach closer to the Rapanos plurality for wetlands, underscoring Rapanos's role as the pivot point in the Court's narrowing of CWA jurisdiction.
Rapanos v. United States is a cornerstone of modern CWA jurisprudence, not because it resolved the meaning of WOTUS, but because its fractured opinions framed the central legal and scientific questions for the next generation. The plurality's textual limits and Kennedy's functional significant nexus test defined the field of battle for courts, agencies, and practitioners.